CN106465370B

CN106465370B - Base station device, control method, and program

Info

Publication number: CN106465370B
Application number: CN201580023938.8A
Authority: CN
Inventors: 彭海兰; 山本俊明; 王晓秋
Original assignee: KDDI Corp
Current assignee: KDDI Corp
Priority date: 2014-05-07
Filing date: 2015-05-07
Publication date: 2020-01-03
Anticipated expiration: 2035-05-07
Also published as: US20170079029A1; JP6366990B2; WO2015170476A1; US10863491B2; EP3142441A4; US10405302B2; JP2015216418A; EP4084394A1; CN106465370A; EP3142441A1; US20190342881A1; EP3142441B1

Abstract

When one terminal device is connected to a base station device and another base station device, a frequency band of a control channel transmitted from the terminal device to the another base station device is selected by the another base station device from a plurality of frequency bands usable by the another base station device, and in a wireless communication system in which the terminal device is notified of the selected frequency band, the base station device: the method comprises acquiring information on the radio quality of a signal received from the other base station device with respect to one or more of the plurality of frequency bands from the terminal device, extracting a partial frequency band from a plurality of frequency bands based on the acquired information on the radio quality, and notifying the other base station device of information characterizing the partial frequency band.

Description

Base station device, control method, and program

Technical Field

The present invention relates to a base station apparatus, a control method thereof, and a program, and particularly to a wireless communication system including a plurality of base station apparatuses and a terminal communicating with the plurality of base station apparatuses.

Background

In the third generation partnership project (3GPP), there is debate about installing multiple small cells (microcells) using different frequency bands (e.g., frequency bands higher than the frequency band used by the macrocell) within the coverage of a large cell (macrocell). For example, as in the example of fig. 1, a plurality of small cells using the 3.5GHz band are provided within the coverage of a macro cell using the 2GHz band.

In LTE Release12, a technique called Dual Connectivity (Dual Connectivity) has been discussed, in which two types of base stations are connected under such an environment (non-patent document 1). Two types of base stations are primary enodebs (primary enbs, e.g., macro cell base stations) and secondary enodebs (secondary enbs, e.g., small cell base stations). In dual connectivity, the two types of base stations are connected by wired or wireless backhaul channels. Note that the terminal device may establish a connection between both the primary eNB and the secondary eNB, such as receiving data from both base station devices.

In dual connectivity, the master eNB signals downlink control signals for the terminal devices. On the other hand, in the uplink, it is assumed that a control signal from the terminal is transmitted not only to the master eNB but also to the slave eNB. The master eNB and the secondary eNB may each use a plurality of frequency bands having a predetermined frequency bandwidth, and the terminal device transmits a control signal in at least any one of the plurality of frequency bands. Each of the multiple bands corresponds to a component carrier of 20MHz bandwidth, for example. In addition, each of a plurality of sections of frequency bands that can be used by each of the master eNB and the secondary eNB is allocated, for example, a unit for a different baseband, and a different unit (communicable range) is formed in each of the plurality of sections of frequency bands. That is, the master eNB and the slave eNB are each one base station device, but form a plurality of units corresponding to a multi-segment frequency band. The set of multiple elements for the master eNB is referred to as a master element group mcg (master Cell group), and the set of multiple elements for the secondary eNB is referred to as a secondary element group smcg (secondary Cell group).

Documents of the prior art

Non-patent document

Non-patent document 1: 3GPP TR 36.842v12.0.0

Disclosure of Invention

Technical problem to be solved by the invention

The terminal device needs to transmit a control channel (PUCCH: physical uplink control channel) to the master eNB and the secondary eNB in one unit of MCG and one unit of SCG. Therefore, the master eNB and the secondary eNB need to determine and notify the terminal device of the unit that needs to transmit the control channel.

In this regard, when the 3GPP is in agreement, the secondary eNB determines that the secondary eNB agrees with one of the terminal devices that transmits the PUCCH included in the plurality of elements included in the SCG. There is also a consensus that the secondary eNB can obtain assistance from the master eNB at this time. However, it has not been established what assistance the secondary eNB gets from the master eNB, how to select the one unit and the detailed method described above.

The present invention is directed to considering the above problems and providing a method for determining one unit for transmitting PUCCH by a secondary eNB in dual connectivity.

Means for solving the problems

According to a base station apparatus of one aspect of the present invention, when one terminal apparatus is connected to a base station apparatus and another base station apparatus, a frequency band of a control channel transmitted from the terminal apparatus to the another base station apparatus is selected by the another base station apparatus from a plurality of frequency bands usable by the another base station apparatus, and in a wireless communication system in which the terminal apparatus is notified of the selected frequency band, the base station apparatus includes: an acquisition unit that acquires information on the radio quality of a signal received from the other base station device with respect to one or more of the plurality of frequency bands from the terminal device, an extraction unit that extracts a partial frequency band from a plurality of frequency bands based on the acquired information on the radio quality, and a notification unit that notifies the other base station device of information characterizing the partial frequency band.

According to a base station apparatus of another aspect of the present invention, when one terminal apparatus is connected to a base station apparatus and another base station apparatus, a frequency band of a control channel transmitted from the terminal apparatus to the another base station apparatus is selected by the another base station apparatus from a plurality of frequency bands usable by the another base station apparatus, and in a wireless communication system that notifies the terminal apparatus of the selected frequency band, the base station apparatus has: an acquisition unit that acquires information on the radio quality of a signal received from the other base station device with respect to one or more frequency bands among the plurality of frequency bands from the terminal device, and a notification unit that notifies the other base station device of the acquired information on the radio quality based on one of the one or more frequency bands.

Effects of the invention

According to the present invention, there is provided a method for determining one unit for transmitting a PUCCH by a secondary eNB in dual connectivity.

Features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

Fig. 1 is a conceptual diagram showing an example of a configuration of a macro cell and a small cell using different frequency bands, respectively;

fig. 2 is a conceptual diagram illustrating an example of communication between a terminal and a plurality of enbs through dual connectivity;

fig. 3 is a diagram showing an example of hardware configurations of a master eNB and a secondary eNB;

fig. 4 is a block diagram showing an example of a functional configuration of a master eNB;

fig. 5 is a block diagram showing an example of a functional configuration of a secondary eNB; and

fig. 6 is a sequence diagram showing an example of the processing procedure.

Detailed Description

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

(System configuration)

For example, as shown in fig. 2, the wireless communication system according to the present embodiment includes a master eNB, a secondary eNB, and a terminal equipment (UE). Note that even though the eNB is a base station equipment (eNodeB) here, the compatible wireless communication system may be any wireless communication system other than LTE. The terminal device is a mobile or fixed wireless communication system, and may be compatible with wireless communication systems other than LTE. Note that according to the wireless communication system in the present embodiment, the master eNB communicates using the first frequency band (e.g., 2GHz), and the slave eNB communicates using the second frequency band (e.g., 3.5 GHz). The primary eNB and the secondary eNB may use the same frequency band, i.e., the first frequency band and the second frequency band may be the same frequency band. Note that even if the first frequency band and the second frequency band are different frequency bands, they may exist as partial frequency bands within the same frequency band as the 2GHz band.

In a frequency band used by each of the master eNB and the secondary eNB, communication can be performed using a plurality of Component Carriers (CCs). Each Component Carrier (CC) of the plurality of CCs corresponds to a frequency band having a predetermined width, such as 20 MHz. As described above, the master eNB and the secondary eNB form a plurality of units that can communicate based on the respective plurality of component carriers. Since one cell corresponds to one component carrier, the term "cell" hereinafter has the meaning of a corresponding CC (frequency band). Note that the following discussion, the frequency band corresponding to each cell need not always correspond to one CC, and may correspond to a frequency band having a predetermined bandwidth defined in the wireless communication system.

As described above, the unit set formed by the master eNB is referred to as MCG (master group), and the unit set formed by the secondary eNB is referred to as SCG (secondary group). Fig. 2 shows a state where each MCG and each SCG includes five cells. The number of cells is determined by, for example, the frequency bandwidth available to each of the primary eNB and the secondary eNB and the frequency bandwidth of one CC. Communication is performed between the master eNB and the terminal using at least one element in the MCG. Similarly, in a state where the dual connectivity is established, communication is performed between the secondary eNB and the terminal using at least one element in the SCG.

In dual connectivity, communication in the C-plane, e.g., transmission of RRC (radio resource control) information to be transmitted to a terminal, is performed by a master eNB, not by a secondary eNB. A unit that performs communication between the master eNB and the terminal in the control plane is referred to as PCell. In the PCell, communication of U-plane (user plane) and in addition to communication in the control plane may be performed. The PCell is set for the terminal, e.g., in the PCell set by itself, the terminal is guaranteed to be able to transmit uplink data to the master eNB. Note that in another cell, the terminal may also transmit uplink data, however, for example, in the set PCell, the terminal does not transmit information, and does not transmit information in another cell. Further, the terminal needs to transmit PUCCH (physical uplink control channel) in PCell. For one or more of the units included in the MCG and the units included in the SCG, the terminal may measure the radio quality of a radio signal transmitted from the primary eNB or the secondary eNB and inform the measurement result to the primary eNB in the PCell. Note that the radio quality may be a Reference Signal Received Power (RSRP) or a reference signal received quality (RSRP), however, in addition to this, another radio quality (e.g., SIR or SNR) may be used as the radio quality. Note that when a predetermined condition is satisfied, for example, when a radio signal from a cell in the SCG is received at a power above a predetermined power, the terminal may notify the master eNB of the measurement result, for example, the terminal may periodically notify the master eNB of the measurement result. In addition, the MCG includes, for example, a serving unit for downlink to the terminal, and the master eNB may transmit data to the terminal in the serving unit for downlink.

On the other hand, the SCG does not include a unit for transmitting RRC information, such as PCell, but sets a unit for transmitting PUCCH from a terminal to each terminal. This unit is referred to herein as the primary scell (pscell). Note that even in a cell other than the pSCell, the terminal can transmit the PUCCH. However, the terminal does not need to transmit the PUCCH in a cell other than the pSCell, and needs to transmit the PUCCH in the pSCell. The SCG also includes a service unit for downlink in which data can be transmitted to the terminal, as in the MCG. In the MCG and SCG, not all cells are used to communicate with the terminal, and for example, as shown by the open square in fig. 2, there are also cells that do not correspond to any one of the PCell, the pSCell, and the serving cell for downlink. For example, neither the master eNB nor the secondary eNB communicates with the terminal in these elements.

(summary)

As described above, the PCell and the pSCell are selected from the MCG and the SCG and set for each terminal, and the setting information is notified to the terminal by RRC information through, for example, the master eNB. As noted above, 3GPP has agreed upon the selection of pSCell from SCG by the secondary eNB. Meanwhile, the secondary eNB may make the selection using the assistance information notified by the primary eNB. However, the detailed method of selection, which information should be used as the auxiliary information, and the like are not currently determined.

Therefore, a detailed method for the secondary eNB to select the pSCell with the assistance of the primary eNB will be mentioned below.

(configuration of Master eNB and Secondary eNB)

Fig. 3 discloses an example of hardware configuration of a master eNB and a secondary eNB (base station apparatus) in the present embodiment. For example, the master eNB and the slave eNB each include a Central Processing Unit (CPU)301, a Read Only Memory (ROM)302, a Random Access Memory (RAM)303, an external storage device 304, and a communication device 305. In each of the master eNB and the slave eNB, the CPU301 records any one of the ROM 302, the RAM 303, and the external storage device 304, and the CPU301 realizes each function of the master eNB or the slave eNB described below.

In each of the master eNB and the slave eNB, for example, communication between the master eNB and the slave eNB and the terminal or intermediate communication of an intermediate eNB between the master eNB and the slave eNB is performed by controlling the communication device 305 by the CPU 301. Note that the primary eNB and secondary eNB may each include dedicated hardware configured to perform each function, alternatively some functions may be performed by hardware and the remainder by a programmed computer. All functions may be performed by a computer and a program.

Note that in fig. 3, the master eNB and the secondary eNB each include one communication apparatus 305, and in fact, a plurality of communication apparatuses may be provided, or the communication apparatus 305 may include a plurality of communication apparatuses. That is, for example, the master eNB and the secondary eNB may each include a communication device for communication between the plurality of enbs and a communication device communicating with the terminal.

Each master eNB and secondary eNB may prepare a communication device for each CC to communicate with the terminal. Note that the communication apparatus 305 may include a plurality of units for baseband processing, and the communication apparatus 305 configures a plurality of CCs to transmit signals generated by the above units through antennas. In this case, for example, identification information (global ID) for uniquely identifying the cell is assigned, whereby it becomes possible to specify one CC for one eNB by the global ID. Note that it is possible to assign one cell ID to each frequency band (CC). In this case, two pieces of identification information including an element ID and an ID for identifying the master eNB are provided, thereby providing one CC for each eNB.

The functional configuration of the master eNB will be described below. Fig. 4 is a block diagram according to an example of the functional configuration of the master eNB in the present embodiment. The master eNB includes, for example, a wireless communication unit 401, a wired communication unit 402, a wireless quality information acquisition unit 403, and a secondary information generation unit 404.

The wireless communication unit 401 is a functional unit configured to perform wireless communication. The wireless communication unit 401 establishes a wireless connection with a terminal, for example, and performs wireless communication. That is, the wireless communication unit 401 establishes communication with a terminal in one or more of the plurality of units included in the MCG. The wireless communication unit 401 selects, for example, one unit from one or more units for establishing communication as a PCell, and the wireless communication unit 401 notifies a terminal of the unit through RRC information. According to the RRC information, the terminal identifies the PCell that needs to transmit the PUCCH. The wireless communication unit 401 receives a PUCCH from a terminal in the PCell. The wireless communication unit 401 also transmits data to a terminal in the PCell or a terminal in a serving unit as used for downlink. In addition to this, the wireless communication unit 401 receives data from a terminal in the PCell or a terminal in another unit out of the PCell. Wireless communication unit 401 may also receive a measurement report including information such as Reference Signal Received Power (RSRP) or reference signal received quality (RSRP) from the terminal. The received measurement report is input to radio quality information acquisition section 403.

The wired communication unit 402 is a functional unit configured to perform wired communication. The wired communication unit 402 establishes wired communication with the secondary eNB, for example, and performs wired communication. The wired communication unit 402 notifies the secondary eNB of the assistance information generated by the assistance information generation unit 404 (to be described later) and uses the assistance information when the secondary eNB selects the PCell, for example. Note that the primary eNB and the secondary eNB may not be connected by wire but by, for example, a fixed wireless channel. In this case, the wired communication unit 402 does not exist. If the radio part exists halfway through the connection between the master eNB and the secondary eNB, the wired communication unit 402 may exist in the form of establishing a wired connection to an endpoint halfway through the radio part.

The radio quality information acquisition unit 403 acquires radio quality on a radio signal received by the terminal for one or more of the plurality of units included in the SCG, which is received by the wireless communication unit 401. That is, the radio quality information acquisition unit 403 acquires information such as RSRP or RSRQ as radio quality at the terminal. Note that the wireless quality information is input to the auxiliary information generating unit 404.

The auxiliary information generating unit 404 generates auxiliary information according to the wireless quality information. The generated assistance information is transmitted to the secondary eNB through the wired communication unit 402. For example, for a unit that acquires radio quality information from a certain terminal, the assistance information generation unit 404 generates assistance information including the radio quality information for each unit. In this case, in order to explicitly show in which cell the radio quality is obtained and for which cell the radio quality is obtained, the identification information of the cell and the radio quality information are associated with each other and included in the auxiliary information. Note that the auxiliary information is generated separately for each of the plurality of terminals, for example. Note that the assistance information generating unit 404 may generate a signal by integrating a plurality of pieces of assistance information corresponding to a plurality of terminals and transmit the signal to the secondary eNB through the wired communication unit 402.

The auxiliary information generating unit 404 may further include, for example, a candidate unit extracting unit 405, where the candidate unit extracting unit 405 extracts a candidate unit selected by the secondary eNB as the pSCell from a part of the plurality of units included in the SCG based on the radio quality information.

Candidate unit extraction section 405 extracts, as a part of the above-described units, a prescribed number of partial units from among a plurality of units in descending order of radio quality included in the SCG, for example, based on the radio quality information. The candidate unit extraction unit 405 extracts units whose wireless quality exceeds a predetermined value as part of the above-described units among the plurality of units included in the SCG based on the wireless quality information. Meanwhile, the number of units whose radio quality exceeds a predetermined value exceeds a predetermined vertical, the candidate unit extraction unit 405 may selectively extract a predetermined number of units. Meanwhile, for example, the candidate unit extraction unit 405 may randomly select a predetermined number of units to extract from among units whose wireless quality exceeds a predetermined value, or selectively extract a predetermined number of units in descending order of wireless quality.

The auxiliary information generating unit 404 generates auxiliary information including information for specifying the extraction partial unit. The information for specifying the cell is, for example, identification information for identifying each cell in the secondary eNB. In this case, identification information of each unit is transmitted to the secondary eNB, and therefore, it becomes possible to specify each unit in the secondary eNB based on a combination of the end point address and the identification information. Similarly, the information specifying the cell may include identification information of the secondary eNB and identification information of the cell. The unit can be uniquely specified based on a combination of the identification information of the secondary eNB and one unit identification information in one secondary eNB. Alternatively, the units in each eNB may be assigned different IDs. If there is identification information capable of uniquely specifying any unit in any eNB, the identification information may be used for information specifying the unit. For example, a set of cells for baseband processing of each cell is assigned a global ID that uniquely specifies that cell pole. Thus, the global ID may be used for information specifying the cell.

The auxiliary information generating unit 404 includes information for specifying the extraction partial units in the auxiliary information in order according to the level of the wireless quality. For example, one extracts a first unit, a second unit, and a fourth unit of five units as an example of the above-described partial units, and the radio quality in the order of decrease of the fourth unit, the first unit, and the second unit will be explained. In such an example, the auxiliary information generation unit 404 contains information that specifies units in the auxiliary information in the order of "4", "1", and "2", for example. Upon receiving the information, the secondary eNB may obtain the fourth unit with the highest radio quality and then obtain the radio qualities of the first and second units in descending order. Therefore, for example, since the fourth unit is considered as the unit having the highest PUCCH reception quality, the secondary eNB selects the fourth unit as the unit to which the terminal transmits the PUCCH. Note that the auxiliary information generation unit 404 may include information that specifies units in the auxiliary information in the order of "2", "1", and "4", for example. Also in such an example, upon receiving the information, the secondary eNB may obtain the fourth unit with the highest radio quality and then obtain the radio qualities of the first and second units in descending order.

Note that the auxiliary information generating unit 404 may generate the auxiliary information by adding information on the order of the levels of the wireless quality of the extracted units. For example, in the example described above, the auxiliary information generating unit 404 may generate the auxiliary information by adding the information "2" of the first unit, the information "3" of the second unit, and the information "1" of the fourth unit. The side information may also include fields such as information containing the radio quality level of each unit. The auxiliary information generating unit 404 may generate the auxiliary information by storing the level of the numerical value in the field. That is, the auxiliary information generating unit 404 may generate the auxiliary information by, for example, "2" in the field of the first unit, "3" in the field of the second unit, and "1" in the field of the fourth unit. Note that as for a unit whose level is lower than a predetermined level, the auxiliary information generation unit 404 may store "0" in a field of the unit.

The auxiliary information generating unit 404 may generate the auxiliary information by including information on the radio quality of the extracted unit section. That is, for example, in the case where the first unit, the second unit, and the fourth unit are extracted as the unit parts described above among five units, the auxiliary information is generated as by RSRP values and RSRQ values of these units. Note that values other than RSRP and RSRQ may be used as the radio quality. In this case, since the level of the wireless quality becomes clear based on the wireless quality information, it is not necessary to include the information of the above level. However, this information may be included. This is because the primary eNB may not know how the secondary eNB uses the assistance information.

The functional configuration of the secondary eNB will be described below. Fig. 5 is a block diagram illustrating an embodiment according to a functional configuration example of a secondary eNB. For example, the secondary eNB includes a wireless communication unit 501, a wired communication unit 502, an assistance information acquisition unit 503, and a pSCell selection unit 504.

The wireless communication unit 501 is a functional unit configured to perform wireless communication. The wireless communication unit 501 establishes wireless communication with a terminal and performs wireless communication, for example. That is, the wireless communication unit 501 establishes communication with the terminal in one or more of the plurality of units included in the SCG. For example, in one pSCell selected by the pSCell selection unit 504 from one or more units for establishing a connection, the wireless communication unit 501 receives PUUCH from a terminal. In the pSCell or the serving cell for downlink, the wireless communication unit 501 also transmits data to the terminal. In the pSCell or another unit other than the pSCell, the wireless communication unit 501 also receives data from the terminal.

The wired communication unit 502 is a functional unit configured to perform wired communication. The wired communication unit 502 establishes wired communication with and performs wired communication with, for example, a master eNB. For example, the wired communication unit 502 receives data such as assistance information transmitted from the master eNB. Note that the master eNB and the secondary eNB are not connected by a wired connection but by a radio channel, such as a radio portal, for example. In this case, the wired communication unit 502 may not be present. The wired communication unit 502 may exist for establishing a wired connection with an endpoint of a midway radio section if the radio section exists midway in the connection between the master eNB and the secondary eNB.

The assistance information acquisition unit 503 acquires assistance information from, for example, a signal received from the master eNB via the wired communication unit 502. The obtained auxiliary information is input to the pSCell selection unit 504. Note that the assistance information acquisition unit 503 may wait for the arrival of assistance information from the master eNB. In some cases, the assistance information acquisition unit 503 may specify a terminal and request the master eNB to transmit assistance information for the terminal.

Based on the input assistance information, the pSCell selection unit 504 selects pSCell, which is a terminal corresponding to the assistance information, from among a plurality of cells included in the SCG. For example, if the assistance information includes information for specifying that a part of cells is extracted from the master eNB among a plurality of cells included in the SCG, the pSCell selection unit 504 selects pSCell among the extracted part of cells. The pSCell selection unit 504 may, for example, select a cell having the highest radio quality as the pSCell if the auxiliary information shows the level of radio quality of the extracted partial cell. For example, if the number of terminals that can select the cell with the highest radio quality as the pSCell is made a predetermined number or more, the pSCell selection unit 504 may select the cell with the second highest radio quality as the pSCell.

The pSCell selection unit 504 may select a pSCell from units whose value of radio quality is a predetermined value or more if the assistance information includes radio quality information such as RSRP and RSRQ values in each unit. Alternatively, the pSCell selection unit 504 may preferably include selecting pSCell among the units of the highest level of radio quality in the auxiliary information. That is, if the number of terminals that select the cell with the highest radio quality as the pSCell is a predetermined number or more, the pSCell selection unit 504 may select the cell with the second highest radio quality as the pSCell. Note that if the terminal measures the radio quality of all units in the SCG, the assistance information may include the measurement value. Even in this case, the pSCell selection unit 504 may select pscells in descending order of wireless quality value, or select a unit having a wireless quality value of a predetermined value or more as a pSCell.

Information of the unit selected by the pSCell selection unit 504 may be notified to the master eNB through, for example, the wired communication unit 502. Note that the pSCell selection unit 504 may control the wireless communication unit 501 according to the selected unit.

Upon receiving information of the selected cell through the wired communication unit 402, the master eNB generates RRC information and transmits the generated RRC information to the terminal through the wireless communication unit 401 to set the pSCell.

(treatment Process)

A processing procedure performed by each of the master eNB, the secondary eNB, and the terminal in wireless communication will be described below. Fig. 6 is a sequence diagram showing an embodiment according to an example of a processing procedure. Note that at the beginning of the process shown in fig. 6, connection setup is completed between the terminal and the master eNB, including which cell of the plurality of cells contained in the MCG should be the pSCell.

In this process, the terminal first monitors the radio signals received from the master eNB and the slave eNB, and measures the radio quality (step S601). Note that radio quality measurements may be made for one or more units contained in the MCG and one or more units contained in the SCG. Here, it is sufficient to mainly perform a radio quality test on the units included in the SCG. The measurement may be made when a predetermined event occurs, for example, when the terminal enters the range of the cell formed by the secondary eNB. Note that the predetermined event is determined by the settings of the wireless communication system, and it is apparent that the event is not limited to the terminal entering the range of the cell formed by the secondary eNB. Then, the terminal notifies the master eNB of the radio quality measured at least for the SCG (step S602). Note that the radio quality notification is performed in the PCell included in the MCG.

When the radio quality information is obtained, the primary eNB then generates the secondary information, which the secondary eNB will use to select the PCell (step S603). Meanwhile, the auxiliary information includes information on, for example, a predetermined number of units specified in descending order for the wireless quality of the wireless signal received by the terminal. The side information may be information for specifying a unit of which wireless quality exceeds a predetermined value. The side information may be information for specifying selection of a predetermined number of units from among the units each having a radio quality greater than a predetermined value if the number of units is a predetermined number or more. The information for specifying a unit may be information as described above in several examples. For example, the information may be a global ID for uniquely specifying a unit set of baseband processing corresponding to the unit. Note that if the auxiliary information includes information for specifying a plurality of cells, the auxiliary information may be generated by including information for specifying the cells in a certain order according to the level of wireless quality of each cell. The assistance information may be generated by a radio quality value (RSRP or RSRQ) measured by the terminal for each element contained in the SCG. In this case, if the radio quality of some units is not measured, a value equal to that in the case where the radio quality is the minimum value may be included as the radio quality information for some units. The assistance information may contain radio quality information for a predetermined number of units or contain radio quality information each including information for units having a radio quality exceeding a predetermined value. The radio quality information of the remaining units may not be included. After that, the master eNB notifies the generated assistance information to the secondary eNB (step S604).

Using the notified assistance information, the secondary eNB selects pSCell, which is a terminal that needs to transmit PUCCH in the cell (step S605). The secondary eNB need not always use the notified assistance information, and may use the assistance information or not apply the assistance information in some cases. For example, if the reliability of the radio quality information used to generate the assistance information is low, it may be the case that the assistance information is not used by the secondary eNB. In this case, the master eNB determines the above-described reliability information based on the reception quality of the radio signal used for the radio quality notification in step S602 or the like, and notifies it to the secondary eNB. Alternatively, whether the secondary eNB should use the assistance information notified by the master eNB may be determined according to the configuration of the secondary eNB.

Note that pSCell selection may be performed again on a terminal that has already set pSCell. That is, the above selection may be made to set the pSCell again in the terminal based on the wireless quality of the wireless signal from each cell in the SCG of each terminal. Meanwhile, the secondary eNB may also select an element (secondary SCell or SCell) for communication with the terminal.

When selecting a pSCell, the secondary eNB notifies the master eNB of information representing the selected pSCell (step S606). Note that if the scell is determined in step S605, the primary eNB may also be notified of information representing the scell by the notification. The notification may be sent as, for example, an inter-eNB RRC message.

Upon receiving the notification of the information representing the pSCell for a certain terminal, the master eNB transmits RRC information (for example, RRC connection reconfiguration message) to set up a radio connection for the terminal (step S607). With this information, the terminal is notified of information indicating the pSCell from which the terminal should transmit the PUCCH. After that, the terminal performs wireless communication setup to transmit the PUCCH in the notified pSCell. In accordance with the completion of the wireless communication setting, the terminal transmits, for example, RRC connection reconfiguration complete message (rrcconnectionreconfiguration complete message) (step S608), and the process ends.

As described above, in this particular embodiment, the master eNB generates assistance information for use by the secondary enbs in selecting the pSCell for the terminal based on the radio quality measured by the terminal. The secondary eNB receives the assistance information provided by the primary eNB and selects the pSCell based on this information. Using this method, the pSCell can be selected so that the communication quality of the PUCCH transmitted from the terminal to the secondary eNB becomes high.

The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to assess the scope of the invention, the following claims are disclosed. The present application claims the benefit of japanese patent application No.2004-096197, filed 5, 7, 2014, the entire contents of which are incorporated herein by reference.

Claims

1. A base station apparatus, wherein when one terminal apparatus is connected to a base station apparatus and another base station apparatus, a frequency band of a control channel transmitted from the terminal apparatus to the another base station apparatus is selected by the another base station apparatus from a plurality of frequency bands usable by the another base station apparatus, and in a wireless communication system in which the terminal apparatus is notified of the selected frequency band, the base station apparatus has:

an acquisition unit that acquires information on the radio quality of the signal received from the other base station device with respect to the plurality of frequency bands from the terminal device,

An extracting unit that extracts one or more frequency bands from the plurality of frequency bands so that the wireless quality of the extracted frequency bands is higher than that of the unextracted frequency bands, and

a notification unit that notifies information characterizing the one or more frequency bands to the further base station device.

2. The base station apparatus according to claim 1, wherein the extracting unit extracts a predetermined number of frequency bands as the one or more frequency bands from a frequency band of high radio quality among the plurality of frequency bands.

3. The base station apparatus according to claim 1, wherein the extraction unit extracts, as the one or more frequency bands, a frequency band having a radio quality greater than a predetermined value from the plurality of frequency bands.

4. The base station apparatus according to claim 3, wherein if the number of frequency bands whose radio quality is larger than the predetermined value is larger than a predetermined number, the extracting unit selects and extracts the predetermined number of frequency bands from the frequency bands whose radio quality is larger than the predetermined value.

5. The base station apparatus according to claim 1, wherein in the base station apparatus, when the identification information characterizing the one or more frequency bands is transmitted to the other base station apparatus, the information characterizing the one or more frequency bands specifies the one or more frequency bands.

6. The base station device of claim 1, wherein the information characterizing the one or more frequency bands comprises information for specifying the further base station device and identification information characterizing the one or more frequency bands.

7. The base station apparatus according to claim 1, wherein if there is different identification information for each of a plurality of base station apparatuses and a combination of each of a plurality of pieces of frequency bands that the plurality of base station apparatuses can use, the information characterizing the one or more frequency bands includes identification information for uniquely specifying a corresponding combination of the other base station apparatus and each of the pieces of information characterizing the one or more frequency bands.

8. The base station device of claim 1, wherein the information characterizing the one or more frequency bands comprises information characterizing the one or more frequency bands in order of wireless quality level.

9. The base station device of claim 1, wherein the information characterizing the one or more frequency bands comprises information about radio quality of the one or more frequency bands.

10. The base station apparatus according to claim 1, wherein the information on the radio quality includes at least one of reference signal received power and reference signal received quality.

11. A control method of a base station apparatus, wherein when one terminal apparatus is connected to a base station apparatus and another base station apparatus, a frequency band of a control channel transmitted from the terminal apparatus to the another base station apparatus is selected by the another base station apparatus from a plurality of frequency bands usable by the another base station apparatus, and in a wireless communication system in which the terminal apparatus is notified of the selected frequency band, the control method of the base station apparatus comprises:

acquiring information on radio quality of a signal received from the other base station apparatus with respect to the plurality of frequency bands from the terminal apparatus,

Extracting one or more frequency bands from the plurality of frequency bands such that the wireless quality of the extracted frequency bands is higher than the wireless quality of the unextracted frequency bands, an

Notifying the further base station device of information characterizing the one or more frequency bands.